Sharks with cameras attached to their fins reveal surprising behavior

Instruments strapped onto – and in some cases swallowed by – sharks are shedding new light on how sharks swim, eat, live, and interact with other marine life.

Thanks to some innovative technology, details about the lives of the most mysterious underwater creatures are now coming to the surface.

Apparently, researchers have found that different species of sharks congregate together, challenging the widely held image of sharks keeping to themselves, or at least sticking with their own kind, says Kim Holland, a researcher at the Hawaiʻi Institute of Marine Biology, who was involved with the study.

Scientists also learned that sharks frequently use powered swimming, instead of gliding, to move through ocean waters.  

To learn about the sharks' lives, researchers from the Hawaiʻi Institute of Marine Biology and the University of Tokyo equipped several sharks from five different species with video cameras and instrument packages. These packages are like "flight data recorders," says Carl Meyer, an assistant researcher at the Hawaii Institute of Marine Biology at the University of Hawaii at Manoa. The instruments recorded details such as the speed, temperature, and body orientation of sharks.

The packages were strapped to their pectoral fins, and were set to detach from the animals after one week, Dr. Meyer says. The packages then floated to the surface and sent out radio signals that allowed researchers to find them. 

The method, says Meyer, gave them a "shark's eye" view of how the fish formed into and disbanded schools. This study was carried out among wild sharks.

But to learn about the food habits of sharks, researchers studied captive sharks, who swallowed small computers fitted with various sensors that are 2.5 inches long; an inch wide and half an inch thick – roughly the size of a lighter, says Dr. Holland.

The researchers got the sharks to ingest these computerized tags by placing them into the body cavities of smaller fish that they fed to the sharks. The sharks couldn't actually digest the tags, so they regurgitated them after a while. While the tags were in the sharks' stomachs, they measured the electrical conductivity of the stomachs' contents.

As of now, it is easy for the scientists to look within the pen and locate the tags. The researchers say that they hope to develop a tag that can be monitored via satellite.

Through this study, scientists are trying to get "a much deeper understanding of sharks’ ecological role in the ocean, which is important to the health of the ocean and, by extension, to our own well-being," said Meyer in a press release.